1. Field of the Invention
The present invention relates to printing apparatuses to form images on sheets transferred on a transfer route. In particular, the present invention relates to a printing apparatus having a decurl function to prevent printed sheets from curling and relates to a printing method of the printing apparatus.
2. Description of Related Art
In a printing apparatus such as an inkjet printer, printed sheets are curled The reason is because a printed side of each sheet becomes wet by adhesion of water-based ink used in the printing apparatus. However, sheet curling is gradually lessened since ink on the sheets is dried as time passes. Thus, there has been proposed a method to decurl the printed sheets without immediately discharging the printed sheets, and to discharge the printed sheets after the dryness of ink.
As a conventional method to secure time to dry ink, Japanese Patent Laid-Open Publication No. 2006-264828 discloses a method to circulate printed sheets on a circulation transfer route in a printer. The method determines a circulation number of the printed sheets according to printing conditions and circulates the printed sheets the determined number of times.